U.S. patent application Ser. No. 683,775 describes a dipper for receiving and screening fine and coarse constituents of collected rock. The dipper has openings in its sides and is mounted on an excavator so as to be elevated. Screening takes place in that the fine constituents drop out of the openings.
U.S. Pat. No. 3,072,257 and UK Pat. No. 1,291,555 describe screening buckets subjected to reciprocating rocking and tilting movements for an increased screening effect. U.S. Pat. No. 3,461,968 describes a screening scoop which is vibrated for an increased screening effect.
The problem of subjecting screening or separating buckets to reciprocating shaking or vibrating movements is that these movements are transmitted to the frame and/or the vehicle on which the bucket is mounted. As a result, violent shaking movements and/or vibrations are transmitted to the equipment and/or personnel. Such vibrations and shaking movements create very great risk of material fatigue and/or bodily injury. The risk increases as the shaking movements increase for further improvement of the separating effect. Intense shaking movements and/or vibrations also generate inconvenient noise.
International Patent Application WO No. 82/01022 teaches a pivotal movement of buckets for setting a bucket into various positions relative to an initial position. The pivotal movement setting the bucket into various angular positions is intended to permit the bucket to be set for excavating both horizontal and inclined areas. It does not provide any solution to the problems of eliminating troublesome shaking movements, vibrations and noise in separating work.